类的练习（设计定义并实现complex类）

一开始的版本

#include<iostream>
#include<cmath>
#include<cstdlib>
using namespace std;
class Complex {
public:
    Complex(double newr = 0, double newi = 0);//此处因为题目要求，Complex c1(3,5)和Complex c2 = 4.5，两种定义方式，我发现只写这一行不够
    Complex(){                                //于是加了一个无参数，同样作用的构造函数Complex，利用了构造函数的重载，这样就可以实现要求的这两行了。
        real = 0;
        imaginary = 0;
    }
    Complex(Complex &c1);
    void add(Complex c1);
    void show();
    double mod();
private:
    double real;
    double imaginary;
};
//构造函数
Complex::Complex(double newr, double newi) 
{
    real = newr;
    imaginary = newi;
}
//复制构造函数
Complex::Complex(Complex &c1) 
{
　　real=c1.real;
　　imaginary = c1.imaginary;
}
//复数相加
void Complex::add(Complex c1) {
    real += c1.real;
    imaginary += c1.imaginary;
}
//输出
void Complex::show() {
    if (imaginary != 0)
        cout << real << "+" << imaginary << "i" << endl;
    else
        cout << real << endl;
}
//取模
double Complex::mod() {
    return sqrt(real*real + imaginary * imaginary);
}
int main() {
    Complex c1(3,5);
    Complex c2 = 4.5;
    Complex c3(c1);
    Complex c4;                      //但是这里会出现问题，因为函数的重载无法判断c4是由第一个还是第二个构造函数定义的，所以此处实现不了
    c1.add(c2);
    cout << "c1=";
    c1.show();
    cout << "c2=";
    c2.show();
    cout << "c3=";
    c3.show();
    cout << "c4=";
    c4.show();
    cout << "c1.mod="<<c1.mod()<<endl;
    system("pause");
    return 0;
}

然后研究了一下怎么才能写一个构造函数而两种定义方法通用

修改版

#include<iostream>
#include<cmath>
#include<cstdlib>
using namespace std;
class Complex {
public:
    Complex(double newr = 0, double newi = 0);
    Complex(Complex &c1);
    void add(Complex c1);
    void show();
    double mod();
private:
    double real;
    double imaginary;
};
//构造函数
Complex::Complex(double newr, double newi) :real(newr), imaginary(newi) {}//利用函数初始化列表
//复制构造函数
Complex::Complex(Complex &c1) : real(c1.real), imaginary(c1.imaginary) {}//利用函数初始化列表
//复数相加
void Complex::add(Complex c1) {
    real += c1.real;
    imaginary += c1.imaginary;
}
//输出
void Complex::show() {
    if (imaginary != 0)
        cout << real << "+" << imaginary << "i" << endl;
    else
        cout << real << endl;
}
//取模
double Complex::mod() {
    return sqrt(real*real + imaginary * imaginary);
}
int main() {
    Complex c1(3,5);
    Complex c2 = 4.5;
    Complex c3(c1);
    Complex c4;
    c1.add(c2);
    cout << "c1=";
    c1.show();
    cout << "c2=";
    c2.show();
    cout << "c3=";
    c3.show();
    cout << "c4=";
    c4.show();
    cout << "c1.mod="<<c1.mod()<<endl;
    system("pause");
    return 0;
}

https://blog.csdn.net/yu132563/article/details/80103887

但是在这篇文章中，函数体内初始化和函数初始化列表应该是相同的作用，并没有什么区别，我也没有搞懂为什么用了初始化列表就可以这么做了，望各位看官解答一下(˘•ω•˘)

                                        ----X.Raven